1. Field of the Invention
The present invention relates to drive circuits for piezoceramic devices, and, more particularly, to a drive circuit for a piezoceramic device capable of providing a controlled variable load current to an output device.
2. Description of the Prior Art
Previous circuits utilizing piezoceramic couplers as isolation between the control and load circuits are intended for triggering electronic power switches. Thus, the piezo device is driven at a fixed frequency and primary voltage to provide pulses for electronic devices. Such prior art methods of switching the primary voltage of a piezoelectric device do not lend themselves to variable load current control which is required for controlling the output of loads such as fluorescent lamps connected to electronic ballasts.
The relative size and cost of a piezoceramic coupler makes the device an attractive replacement for a magnetic isolation transformer. However, a 10 kilohertz control signal normally required for an electronic ballast is not within the bandwidth limitations of most piezoceramic couplers. Therefore, a design is needed for a circuit that can perform functionally as a source of an electronic ballast control signal switched at the coupler's resonance frequency.